Use

Potassium (K+) is the major intracellular cation with important functions in the body, including regulation of neuromuscular excitability, heart contractility, intracellular fluid volume, and hydrogen ion concentration. The kidneys are responsible for regulating potassium levels, with most filtered potassium being reabsorbed in the proximal tubules. The test is useful for determining the cause of hyper- or hypokalemia, and helps in assessing renal function particularly distal nephron function in potassium excretion.